There was no evidence that the captain was "fastidious", apart from the evidence that he was dead and the social requirement to not speak ill of such people. If anything, he was the opposite. (I don't adhere to the aforementioned social requirement, which is why Mahon was an idiot.)
The crew could not have received any briefing of the sort 3 Holer describes outside the 30 minutes caught on tape. The is obvious from reading the transcript (whatever version):
Cloud come down - May have to miss McMurdo. No reference to going down VMC - which there would have been if 3 Holer were correct.
Radar assist offered. Great! Announce it to the passengers.
Ten minutes trying to contact the radar operator on VHF. No luck. Then, out of the blue, the captain says he can see the ground, that he is going to do an orbit, and that he is descending VMC.